The construction of buildings is facilitated by using walling elements in the form of thin concrete panels. These concrete panel wall elements are most commonly cast in the horizontal position. Panels are often manufactured in factories after which the panels must be transported to the job site for erection. The size of these panels is restricted by the largest size capable of being transported. Economies can be achieved using larger panels cast on-site using the so-called “Tilt-up” method where the panels are cast on the floor slab or a casting bed and erected directly into position as wall elements.
In all cases, the horizontally cast panels must first be tilted up from the horizontal position to the vertical position for their erection as wall panels of the building.
Preferably the panels are lifted by their edges to enable them to be erected in the truly vertical position, however, the stresses induced in the panels as a result of lifting limits the size of panels which can be lifted in this way. When the stresses in the panel exceed the panel strength, the panel must be lifted using an array of anchors cast into the face of the panel. This is most commonly used for the erection of large tilt-up panels.
The smaller panels manufactured in factories can be tilted up from the moulds using anchors located in the edges of the panels. After rotation to the vertical, the panels can be transported around the building site and easily erected in all situations because they hang truly vertically. This is particularly advantageous for panels which are to be attached to framework or other building structures or erected against other components.
Releasable lifting links for connection between embedded lifting anchors and the hoisting chains are known. One known type of link is that disclosed in U.S. Pat. No. 3,883,170 and is used to connect to the head of an anchor having a generally planar body which is embedded in concrete. This anchor incorporates a through aperture to which a latching device incorporated within the releasable link attaches. The anchor is cast within a surrounding recess such that the head of the anchor lies below the surface of the concrete thereby protecting it from damage.
The lifting link has the form of a hollow ring, or a toroidal body, a pivotable shackle element for connection to the hoisting system passing through the internal transverse hole of the toroidal body. The lower part of the toroidal body has a transverse slot which enables it to envelope the head of the anchor. An arcuate latching device is fitted to rotate within the hollow arcuate cavity of the toroidal body.
The latching device has a semi-circular configuration and incorporates a radial arm which extends from one end and which facilitates the rotation of the latching device. The upper periphery of the toroidal body is removed to form a U-shaped slot through which the radial arm passes during rotation.
Connection of the lifting link to the anchor is achieved by rotation of the latching device such that it lies within the hollow body in a position where it does not obstruct the transverse slot in the toroidal body. The toroidal body then envelopes the anchor head such that the curved or arcuate axis of the chamber within the hollow toroidal body is aligned with the axis of the aperture in the anchor head. The arcuate latching ring is then rotated within the chamber of the hollow toroidal body so that it passes through the aperture in the anchor head, thereby connecting the anchor to the lifting link.
WO 82/01541 discloses a lifting link adapted for the releasable connection to anchors cast in the face of concrete panels used for tilt-up construction of site cast wall panels.